1. Field of Invention
This invention pertains to a system for monitoring an outdoor perimeter. More particularly, this invention relates to a system for monitoring and distinguishing between occurrences along a perimeter bounded by at least one piezoelectric cable that completely defines the perimeter.
2. Description of the Related Art
Residential and light commercial security systems have become an increasingly popular addition to many homes and businesses. These systems are typically based on the electronic detection of a structure. These systems generally classify any input as an event, whether the input is a system message, a detected breach of a perimeter, a detected breach of an interior, or a failure of some part of the security system. The event is analyzed to determine a specific classification, more specifically whether there has been a breach or not. If an event is determined to be in the nature of a breach, it is further classified as being caused by environmental conditions, an animal, a human, or an automobile.
In a residential and light commercial security system a breach is generally detected at either the perimeter or the interior of the structure. The perimeter is commonly defined as the outer surface of the structure. It is generally breached at the entrance/egress points to a structure such as doors and windows. Breaches at these entrance/egress points are generally detected by magnetic sensors that monitor the opening and closing of doors and windows and by frequency sensors attuned to the sound of glass breakage. Interior breaches are generally detected by heat and motion detectors that monitor moving objects having a temperature greater than the ambient temperature. While providing a warning of intrusion, both the detection of entrance/egress and interior breaches occur after the structure has been damaged or entry has been obtained.
In many security systems, motion sensors are used to turn on outdoor lighting, thereby providing a deterrent to intrusion onto the property. However, these sensors are indiscriminate in that they may be triggered by small animals, children, or other moving objects that are not considered security risks. Further, because of the difficulty in accurately setting the range, and the accurate detection zone of each sensor, setting up a comprehensive coverage area limited to the boundaries of one's property is difficult. Finally, it should be noted that while the external sensors can be connected to a central alarm system, the inability to discriminate between legitimate security risks and stray animals and the difficulty in defining the protection area render such a system unreliable.